U.S. patent number 4,838,556 [Application Number 07/137,649] was granted by the patent office on 1989-06-13 for golf ball core by addition of dispersing agents.
This patent grant is currently assigned to Spalding & Evenflo Companies, Inc.. Invention is credited to Michael J. Sullivan.
United States Patent |
4,838,556 |
Sullivan |
June 13, 1989 |
Golf ball core by addition of dispersing agents
Abstract
Golf balls exhibiting superior durability and improved
coefficient of restitution is provided by the inclusion of a
dispersing agent in the core formulation.
Inventors: |
Sullivan; Michael J. (Chicopee,
MA) |
Assignee: |
Spalding & Evenflo Companies,
Inc. (Tampa, FL)
|
Family
ID: |
22478437 |
Appl.
No.: |
07/137,649 |
Filed: |
December 24, 1987 |
Current U.S.
Class: |
473/372; 524/432;
524/908; 525/274 |
Current CPC
Class: |
A63B
37/0003 (20130101); C08F 279/02 (20130101); C08F
279/02 (20130101); C08F 220/06 (20130101); A63B
37/0064 (20130101); A63B 37/0074 (20130101); A63B
37/0078 (20130101); A63B 37/0083 (20130101); A63B
37/0087 (20130101); Y10S 524/908 (20130101) |
Current International
Class: |
A63B
37/00 (20060101); C08F 279/00 (20060101); C08F
279/02 (20060101); A63B 037/02 (); A63B
037/06 () |
Field of
Search: |
;273/220,230,218
;524/908,430 ;260/998.14 ;525/274 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4305851 |
December 1981 |
Tominaga et al. |
4546980 |
October 1985 |
Gendreau et al. |
4561657 |
December 1985 |
Tominaga et al. |
4683257 |
July 1987 |
Kakiuchi et al. |
4726590 |
February 1988 |
Molitor |
|
Primary Examiner: Lieberman; Allan M.
Attorney, Agent or Firm: Bahr; Donald R.
Claims
What is claimed is:
1. A golf ball comprising a cover and a molded spherical core;
said core comprising a base elastomer selected from polybutadiene
having a molecular weight of from about 50,000 to about 500,000 and
admixtures of said polybutadiene with other elastomers,
at least one metallic salt of an alpha, beta-ethylenically
unsaturated monocarboxylic acid,
a free radical initiator; and
a surfactant dispersing agent, in an amount from about 0.1 to about
5.0 parts by weight per 100 parts of rubber, selected from sulfated
fats, sodium salts of aklylated aromatic sulfonic acids,
substituted benzoid alkyl sulfonic acids, monoaryl and alkyl ethers
of diethylene glycol and dipropylene glycol, ammonium salts of
alkyl phosphates, sodium alkyl sulfates and monosodium salt of
sulfated methyl oleate and sodium salts of carboxylated
eletrolytes.
2. The golf ball as defined by claim 1 wherein said elastomer is
cis-polybutadiene.
3. The golf ball as defined by claim 1 wherein said cover comprises
an ionic copolymer of ethylene and an alpha, beta-ethylenically
unsaturated monocarboxylic acid selected from the group consisting
of acrylic acid and methacrylic acid wherein about 20-90 percent of
the carboxylic acid groups are neutralized by a metal ion.
4. The golf ball as defined by claim 1 wherein said monocarboxylic
acid is selected from the group consisting of acrylic acid,
methacrylic acid, itaconic acid, crotonic acid, sorbic acid and
mixtures thereof.
5. The golf ball as defined by claim 1 wherein crosslinking of said
elastomer and said metallic salt is effected by a free radical
initiator.
6. The golf ball as defined by claim 5 wherein said free radical
initiator is selected from the group consisting of peroxides,
persulfates, hydrazides and azo compounds.
7. The golf ball as defined by claim 1 wherein said core further
comprising a modifying ingredient selected from fillers, metal
oxides, low molecular weight fatty acids, diisocyanates and
mixtures thereof.
8. The golf ball as defined by claim 7 wherein said modifying
ingredient is a low molecular weight fatty acid.
9. The golf ball as defined by claim 8 wherein said fatty acid is
stearic acid.
10. The golf ball as defined by claim 7 wherein said modifying
ingredient is diisocyanate.
11. The golf ball as defined by claim 10 wherein said diisocyanate
is 4,4'-diphenyl methane diisocyanate.
12. The golf ball as defined by claim 7 wherein said modifying
ingredient is metal oxide.
13. The golf ball as defined by claim 12 wherein said metal oxide
is zinc oxide.
14. The golf ball as defined by claim 1, wherein said dispersing
agent is a sodium salt of polymerized alkyl naphthalene sulfonic
acid.
15. The golf ball as defined by claim 1, wherein said dispersing
agent is a sodium salt of polymerized substituted benzoid alkyl
sulfonic acid.
Description
This invention relates to golf balls. More particularly, this
invention relates to multi-ply solid golf balls having a high
impact resilience and an excellent durability.
Wound golf balls which have been widely employed have been
particularly desirable in possessing high impact resilience and
high initial velocity on impact. However, the wound golf balls
suffer a major flaw in lacking durability.
In order to improve the durability, there have been developed
two-piece solid golf balls consisting of a solid core having a good
impact resilience and a cover, either unitary or multi-ply, having
an excellent resistance to cutting.
There are several advantages of homogenous, unitary construction
for a golf ball, in contrast to the wound golf balls of the earlier
art. Unitary golf balls can be produced with an essentially perfect
center of gravity with attendant desirable properties of superior
roll and trueness of flight. Such golf balls are highly resistant
to cutting, often indestructible in normal play, and return to
round even when severely distorted, maintaining their superior
flight characteristics even after extended use.
Additionally, and in contrast to the wound golf balls, unitary
balls maintain the integrity of their playing characteristics
throughout widely varying temperature ranges, will not water log
and possess an excellent shelf life.
While golf balls have found wide acceptance and constitute by far
the bulk of sales, the advantages gained in the properties
enumerated have been offset to a degree by decreased impact
resilience.
It is, therefore, an object of the present invention to provide
unitary golf balls exhibiting superior durability, and an improved
coefficient of restitution.
In accordance with the present invention, there is provided a
unitary golf ball comprising a solid core and a cover therefor, the
solid core comprising an elastomer or admixture of elastomers, at
least one metallic salt of an unsaturated carboxylic acid, free
radical initiator and a dispersing agent.
It has been found that the addition of the dispersing agent to the
core composition and the presence thereof during the cure cycle
results in an increase of the coefficient of restitution of from
about 0.5 to about 2.0 percent over that exhibited by a similar
core prepared in the absence of a dispersing agent.
The core compositions of the prevent invention may be based on
polybutadiene, and mixtures of polybutadiene with other elastomers.
It is preferred that the base elastomer have a relatively high
molecular weight. The broad range for the molecular weight of
suitable base elastomers is from about 50,000 to about 500,000. A
more preferred range for the molecular weight of the base elastomer
is from about 100,000 to about 500,000. As a base elastomer for the
core composition, cis-polybutadiene is preferable employed, or a
blend of cis-polybutadiene with other elastomers may also be
utilized. Most preferably, cis-polybutadiene having a
weight-average molecular weight of from about 100,000 to about
500,000 is employed.
The unsaturated carboxylic acid component of the core composition
is the reaction product of the selected carboxylic acid or acids
and an oxide or carbonate of a metal such as zinc, magnesium,
barium, calcium, lithium, sodium, potassium, cadmium, lead, tin and
the like. Preferably, the oxides of polyvalent metals such as zinc,
magnesium and cadmium are used, and most preferably the oxide is
zinc oxide.
Exemplary of the unsaturated carboxylic acids which find utility in
the present core compositions are acrylic acid, methacrylic acid,
itaconic acid, crotonic acid, sorbic acid and the like, and
mixtures thereof. Preferably, the acid component is either acrylic
or methacrylic acid. Usually, from about 20 to about 50, and
preferaby from about 25 to about 40 parts by weight of the
carboxylic acid salt is included in the core composition.
The free radical initiator included in the core composition is any
known polymerization initiator which decomposes during the cure
cycle. The amount of the selected initiator present is dictated
only by the requirements of catalytic activity as a polymerization
initiator. Suitable initiators include peroxides, persulfates, azo
compounds and hydrazides. Peroxides which are readily commercially
available are conveniently used in the present invention, generally
in amounts of from about 0.1 to about 10.0 parts by weight per each
100 parts of rubber.
Exemplary of suitable peroxides for the purposes of the present
invention are dicumyl peroxide, n-butyl 4,4'-bis (butylperoxy)
valerate, 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane,
di-t-butyl peroxide and 2,5-di-(t-butylperoxy)-2,5 dimethyl hexane
and the like, as well as mixtures thereof.
The dispersing agent of the present core composition may be
anionic, cationic, noionic or amphoteric in properties as a
surfactant. If desired, mixtures of selected dispersing agents may
be used. Suitable dispersing agents include alkali metal salts of
fatty acids having from about 12 to about 20 carbon atoms, such as
caprylic, lauric and stearic acid and the like; sulfated fats such
as sulfated oleic acid, sulfated castor oil, sulfated coconut oil
and the like; sodium salts of alkylated aromatic sulfonic acids
such as naphthalene sulfonic acid, substituted benzoid alkyl
sulfonic acids and the like; monoaryl and monoalkyl ethers of
dialkylene glycols such as monomethyl and monophenyl ether of
diethylene glycol and polyethylene glycol. Additionally, such
dispersing agents as ammonium salts of alkyl phosphates, sodium
salts of carboxylated electrolytes, sodium alkyl sulfates,
monosodium salt of sulfated methyl oleate and the like may be used.
Preferably, the dispersing agent is a sodium salt of polymerized
alkyl naphthalene sulfonic acid or sodium salt of polymerized
substituted benzoid alkyl sulfonic acids such as DARVAN (R. T.
Vanderbilt Co.).
The dispersing agent is included in an amount of from about 0.1 to
about 5.0, preferably from about 0.2 to about 2.0 parts by weight
per 100 parts of rubber.
The core compositions of the present invention may additionally
contain any other suitable and compatible modifying ingredients
including, but not limited to, fillers, metal oxides, fatty acids,
and diisocyanates.
As fillers, any known and conventional filler material, or mixtures
thereof, may be used. Such fillers as are incorporated into the
core compositions should be in finely divided form, as for example,
in a size generally less than about 20 mesh and preferably less
than about 100 mesh U.S. standard size. Suitable fillers include
silica, silicates, zinc oxide, carbon black, cork, titania, cotton
flock, cellulose flock, leather fiber, plastic and/or leather
flour, asbestos, glass fibers, metal carbonates and talc.
Particularly useful is the oxide or carbonate of the cation used in
forming the metal salt of the unsaturated carboxylic acid
component.
The amount of filler included in the core composition is primarily
dictated by weight restrictions and preferably is included in
amounts of from about 10 to about 100 parts by weight per 100 parts
rubber.
Fatty acids may also be included in the compositions, functioning
to improve moldability and processing. Generally, free fatty acids
having from 10 to about 40 carbon atoms, and preferably having from
about 15 to about 20 carbon atoms, are used. Exemplary of suitable
fatty acids are stearic acid and linoleic acids, as well as
mixtures thereof. When included in the core compositions, the fatty
acid component is present in amounts of from about 1 to about 15,
preferably in amounts of from about 2 to about 5 parts by weight
based on 100 parts rubber.
It is preferred that the core compositions include stearic acid as
the fatty acid adjunct in an amount of from about 2 to about 5
parts by weight per 100 parts of rubber.
Diisocyanates may also be optionally included in the core
compositions when utilized, the diisocyanates are included in
amounts of from about 0.2 to about 5.0 parts by weight based on 100
parts rubber. Exemplary of suitable diisocyanates is
4,4'-diphenylmethane diisocyanate and other polyfunctional
isocyanates known to the art.
In producing golf ball cores utilizing the present compositions,
the selected components are intimately mixed using, for example,
two roll mills or a Banbury mixer until the mixture is uniform,
usually over a period of from about 5 to about 20 minutes. The
sequence of addition of components is not critical.
A preferred blending sequence is one wherein rubber, zinc salt,
metal oxide, filler, fatty acid and surfactant are blended for
about 7 minutes in an internal mixer such as a Banbury mixer. As a
result of shear during mixing the temperature rises to about
200.degree. F. The initiator is then added and the mixing continued
until the temperature reaches about 220.degree. F. whereupon the
batch is discharged onto a two roll mill, mixed for about one
minute and sheeted out.
The sheet is then placed in a Barwell preformer and slugs are
produced. The slugs are then subjected to compression molding at
about 325.degree. F. for about 14 minutes. After molding and
cooling, the cooling effected at room temperature for about 4
hours, the molded cores are subjected to a centerless grinding
operation whereby a thin layer of the molded core is removed to
produce a round core having a diameter of 1.545 inches.
Usually the curable component of the composition will be cured by
heating the composition at elevated temperatures on the order of
from about 275.degree. F. to about 350.degree. F., preferably from
about 295.degree. F. to about 325.degree. F., with molding of the
composition effected simultaneously with the curing thereof. The
composition can be formed into the core structure by any one of a
variety of molding techniques, e.g., injection, compression or
transfer molding. When the composition is cured by heating, the
time required for curing will normally be of short duration,
generally from about 10 to about 20 minutes, depending upon the
amounts and activity of the selected curing agent. Those of
ordinary skill in the art of free radical curing agents for
polymers are conversant with adjustments of cure times and
temperatures required to effect optimum results from any specific
free radical agent.
The core is then converted into a golf ball by providing at least
one layer of covering material, ranging in thickness from about
0.050 to about 0.250 inch, preferably from about 0.060 to about
0.090 inch.
The cover composition is preferably made from ethylene-acrylic acid
or ethylene-methacrylic acid copolymers neutralized with mono- or
divalent metals such as sodium, potassium, lithium, calcium, zinc
or magnesium.
While the cover composition may be any of a number of covering
materials known in the art, such as balata, polyolefins and the
like, it is preferred, for imparting durability to the ball, to
employ ionomeric resins, such as those produced by neutralizing the
copolymers described in U.S. Pat. No. 3,421,766 and British Pat.
No. 963,380 using the procedures set out in Canadian Pat. Nos.
674,595 and 713,631. In accordance with the procedures set forth in
the aforementioned patents, the ionomeric resin is produced by
copolymerizing a selected olefin and unsaturated carboxylic acid to
provide a copolymer having the acid units randomly distributed
along the polymer chain, with the relative amounts of reactants
adjusted to provide a copolymer containing from about 9 to about 15
mole percent of the carboxylic acid moiety, at least about 18
percent, preferably from about 18 to about 60 percent of the acid
groups are then neutralized by metal ions having a valence of from
1 to 4, including sodium potassium, zinc, calcium, magnesium, and
the like.
Suitable olefins include ethylene, propylene, butene-1, hexene-1
and the like. Unsaturated carboxylic acids which may be
copolymerized with the selected olefin include acrylic acid,
methacrylic acid, ethacrylic acid, alpha-chloroacrylic acid,
crotonic acid, maleic acid, fumaric acid, itaconic acid and the
like. Preferably, the ionomeric resin is a copolymer of ethylene
with either acrylic or methacrylic acid having from about 9 to
about 15 mole percent acid moiety.
The golf ball can be produced by covering the core using one of
several available methods. For example, a core may be placed in the
center of a golf ball mold and the cover composition injected into
and retained in the surrounding space for a period of time at a
mold temperature of from about 40.degree. F. to about 120.degree.
F.
Alternatively, the cover composition may be injection molded at
temperatures of from about 200.degree. F. to about 450.degree. F.
into smooth-surfaced hemispherical shells, a core enveloped with
two such shells placed in a dimpled golf ball mold at temperatures
on the order of from about 100.degree. F. to about 200.degree.
F.
Coloration of the golf ball may be effected by including a selected
coloring agent uniformly dispersed in the cover composition, or by
applying one or more coatings of paint to the ball after molding.
Indicia is applied to complete the product.
The invention is further described in the following examples
wherein the parts are by weight unless otherwise specified.
EXAMPLES
Employing the ingredients tabled below, golf ball cores having a
finished diameter of 1.545 inches were produced by compression
molding and subsequent removal of a surface layer by grinding. Each
core was formulated using 100 parts high cis content polybutadiene.
In the examples, the amounts of the remaining ingredients are
expressed in parts by weight, and the degrees of coefficient of
restitution and compression achieved set forth.
______________________________________ EXAMPLES Ingredients 1 2 3 4
5 ______________________________________ Zinc Diacrylate 40 40 40
40 40 Zinc Oxide 17 17 17 17 17 Stearic Acid 5.0 5.0 5.0 5.0 5.0
4,4'-diphenyl 1.0 1.0 1.0 1.0 1.0 methane diisocyanate peroxide 1.2
1.2 1.2 1.2 1.2 Dodecanethiol 1.0 1.0 1.0 1.0 1.0 Dispersing Agent
1 -- 1.0 5.0 -- -- Dispersing Agent 2 -- -- -- 1.0 5.0 Weight gms.
37.5 37.6 38.0 37.7 37.2 Compression 55 50 48 47 50 Coefficient of
.805 .814 .803 .816 .797 Restitution
______________________________________ (Dispersing Agent l sodium
salt of polymerized naphthalene sulfonic acid Dispersing Agent 2
sodium salt of polymerized substituted benzoid alkyl sulfonic
acid.)
______________________________________ EXAMPLES Ingredients 6 7 8 9
______________________________________ Zinc Diacrylate 31 3l 31 31
Ground Flash 18 18 18 18 Zinc Oxide 17 17 17 17 Zinc Stearate 20 20
20 20 n-Butyl 4,4-Bis- 0.75 0.75 0.75 0.75 (Butylperoxide) Valerate
Dispersing Agent 1 -- 0.1 0.2 1.0 Dispersing Agent 2 -- -- -- --
Weight gms. 39.9 39.8 39.8 40.0 Compression 62 63 60 63 Coefficient
of .805 .805 .808 .804 Restitution Size 1.545 1.545 1.545 1.545
______________________________________
______________________________________ EXAMPLES Ingredients 10 11
12 ______________________________________ Zinc Diacrylate 31 31 31
Ground Flash 18 18 18 Zinc Oxide 17 17 17 Zinc Stearate 20 20 20
n-Butyl 4,4-Bis- 0.75 0.75 0.75 (Butylperoxide) Valerate Dispersing
Agent 1 -- -- -- Dispersing Agent 2 0.1 0.2 1.0 Weight gms. 40.0
39.9 39.9 Compression 60 62 64 Coefficient of .806 .808 .804
Restitution Size 1.545 1.545 1.545
______________________________________
DISCUSSION OF THE EXAMPLES
The data for examples 1 and 6 represent controls in that the cores
produced in these examples do not incorporate dispersing agents.
The average coefficient of restitution for these control cores is
0.805 with an average compression of 58.5. This difference in
compression is thought to be due to the fact that the formulation
for example 1 is different than that of example 6.
Example 7 uses a dispersing agent at 0.1 parts, it can be seen that
at this low level the use of a dispersing agent in accordance with
this invention is ineffective.
Examples 3 and 5 use a dispersing agent at 5.0 parts, a relative
high concentration which is ineffective, note the significant
decrease in the respective coefficient of restitutions.
Examples 2, 4, 7, 8, 10 and 11 are compositions which use
dispersing agents in accordance with this invention. As we
mentioned above, the average coefficient of restitution for the
control data of examples 1 and 6 is .805. The average coefficient
of restitution for the examples in accordance with this invention
is 809.5 for an increase in the coefficient of restitution of 4.5
points. This increase of 4.5 points is significant in that it
represents an increase of approximately 3 to 6 yards in the
distance which a golf ball will travel when struck under controlled
conditions. This beneficial increase in coefficient of restitution
is achieved while maintaining a relatively constant
compression.
From the above data, it can be seen that the optimum effective
level of dispersing agent used in accordance with this invention
varies from formulation to formulation. One skilled in the art
arrives at the optimum effective level of the dispersing agent for
a given formulation by experimentation. In this regard, see the
data for examples 9 and 12 wherein it can be seen that the use of
dispersing agent 2 in the given formulation peaks at 1.0 parts.
It is to be appreciated that the specification and examples are set
forth by way of illustration and not limitation, and that various
modifications and changes may be made without departing from the
spirit and scope of the present invention.
* * * * *